Introduction to Genetics Chapter 6: Meiosis and Mendel

1. Introduction to GeneticsChapter 6: Meiosis and Mendel Dihybrids and Test Crosses

2. DIHYBRID CROSSES (Involves 2 Traits)

3. Another question Mendel proposed? • Does the gene that determines if a seed is round or wrinkled have anything to do with the gene for seed shape? • Must a seed that is yellow also be round?

4. MAKING A CROSS with ___________________=____________________ TWO gene traits A Punnett square for a DIHYBRID CROSS looks like this: DIHYBRID CROSS

5. Figure 11-10 Independent Assortment in Peas Section 11-3

6. Review: Law of Segregation (Mendel’s first law of genetics • Organisms inherit two copies of each gene, one from each parent • Organisms donate only one copy of each gene in their gametes. • Thus, the two copies of each gene segregate, or separate, during gamete formation

7. INDEPENDENT ASSORTMENT • LAW OF ______________________ the factors are distributed to gametes independently of other factors • Mendel’s second law of genetics Image modified from: http://anthro.palomar.edu/mendel/mendel_1.htm

8. LET’S MAKE A DIHYBRID CROSSR – Yellow Y - Roundr – green y - wrinkled HOMOZYGOUS YELLOW ROUND HOMOZYGOUS GREEN WRINKLED RRYY rryy 1. ___________ what _________________ are 2. ________correct__________ square __________ 3. ______ possible_______________________ 4. ______ boxes with _____________________ 5. Determine ____________of_____________& ____________ Figure out parent alleles Choose Punnett size Put in parent gametes Fill in offspring combinations probabilities phenotypes genotypes

9. PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE? R-yellow, r-green Y-round, y-wrinkled HOMOZYGOUS ROUND YELLOW Each gamete shouldget one of each kindof gene RRYY RY RY RY RY ___________ ____________ _____________ _____________

10. PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE? R-yellow, r-green Y-round, y-wrinkled Each gamete shouldget one of each kindof gene HOMOZYGOUS WRINKLED GREEN rryy r y ry ry ry ___________ ____________ _____________ _____________

11. ry ry ry ry RY RY RY RY RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy RrYy 100% of offspring = _______ genotype _______________________ phenotype ROUND YELLOW

12. MAKE ANOTHER CROSS R-yellow, r-green Y-round, y-wrinkled HETEROZYGOUSROUND YELLOW HETEROZYGOUSROUND YELLOW X RrYy RrYy

13. PRACTICE MAKING GAMETES WHAT ARE THE POSSIBLE GAMETES THIS PARENT CAN MAKE? R-yellow, r-green Y-round, y-wrinkled HETEROZYGOUSROUND YELLOW Each gamete shouldget one of each kindof gene RrYy RY ry rY Ry ___________ ____________ _____________ _____________

14. POSSIBLE PARENT GAMETES? RY rY ry Ry

15. RY Ry rY ry RY Ry rY ry ____ Round & Yellow ____ Round & green ____ Wrinkled & yellow ____ wrinkled & green 9 RRYYRRYyRrYYRrYy RRYyRRyyRrYyRryyRrYYRrYyrrYYrrYy RrYyRryyrrYyrryy 3 3 1 heterozygous dihybrid Sign of a ______________________ cross is a _____________ ratio in offspring. 9:3:3:1

16. 9 ____ ____________ TRAIT 1 ; ____________ TRAIT 2 ____ ____________ TRAIT 1; _____________ TRAIT 2 ____ ____________ TRAIT 1; _____________ TRAIT 2 ____ ____________ TRAIT 1; _____________ TRAIT 2 dominant dominant 3 dominant recessive 3 recessive dominant 1 recessive recessive __________ratio is a clue that it’s a ____________________________cross 9:3:3:1 HETEROZYGOUS TWO gene

17. PRACTICE MAKING GAMETESfor DIHYBRID CROSSES http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html

18. What are the possible gametes?Round-R, Wrinkled-r Tall-T, Short-t pure round & pure tall = __________ ____ ____ _____ ______ What gametes can it produce? R RTT     R T RT RT R T

19. What are the possible gametes?Round-R, Wrinkled-r Tall-T, Short-t Heterozygous Tall = __________ & pure round ____ ____ _____ ______ What gametes can it produce? RRTt     RT Rt RT Rt

20. What are the possible gametes?Round-R, Wrinkled-r Tall-T, Short-t Hybrid tall = __________ & pure wrinkled ____ ____ _____ ______ What gametes can it produce? rrTt     rT rT rt rt

21. What are the possible gametes?Round-R, Wrinkled-r Tall-T, Short-t Heterozygous tall = __________ & hybrid round ____ ____ _____ ______ What gametes can it produce? RrTt     RT rt Rt rT

22. Dihybrid Cross • Dihybrid Cross